Several communication networks are known which can deliver television or audio signals, such as a terrestrial broadcast network, a cable network and a satellite network. Each of these networks can also deliver digital audio-video signals. In addition, it is also possible to deliver digital audio-video signals via a telephone network, e.g., using T1 (or higher capacity lines) and so-called DSL or digital subscriber loop lines.
In each of the networks described above, the audio or audio-video signals (hereinafter, collectively, “program signal(s)”) are intended to be delivered in real-time, i.e., for real-time consumption. Specifically, the program signals are delivered nominally at a rate that matches the consumption (decode and presentation) rate of the signal. Thus, if the program signal is to be displayed at 30 frames per second, the digital information representing the video is nominally delivered at the rate of 30 frames per second. However, in the case that the program signal, or a component elementary stream thereof, such as a video signal, audio signal, closed-caption text signal, etc., is variably compressed, the actual instantaneous bit rate actually fluctuates. Thus, some temporary buffering is required at the receiver/decoder end of the program signal. Such buffer space is of a limited, predetermined size and the flow of digital information through the buffer (more concretely, the time at which each piece of digital information is inputted to or removed from the buffer) is strictly controlled. Therefore, these signals can be considered to be consumed nominally (more or less) at the same rate at which they are delivered.
As noted above, digital program information delivered by one of the above noted networks is variably compressed. For example, video can be compressed according to any of the following standards: MPEG-1, MPEG-2, MPEG-4, H.261, H.263, H.320, JPEG, etc. Likewise, audio can be compressed according to any one of the following standards: “MP3” (MPEG-1 Layer III), MPEG-2, AC-3, AC-4, G.720, ATRAC, “MLP” (Meridian Lossless Packing), Delta-Sigma, etc. If the video is variably compressed, the amount of information needed to represent a “presentation unit” or a given unit of playback time (e.g., a frame or field of video, an audio frame, etc.) varies from presentation unit to presentation unit. Variably compressed signals have timing and scheduling constraints described in the above-noted incorporated applications. Suffice it to say that in a multiplexed signal of one or more programs, each elementary stream has a strict piece-wise time delivery schedule that must be observed to enable proper real-time consumption of a given program. Also, care must be taken to ensure that the relative spacing of time stamps of a given program within a stream is not disturbed too much and that the values of such time stamps are adjusted to reflect any relative movement.
Some of the above networks can also deliver non-real-time data as well as real-time program data. Herein, non-real-time data includes virtually any kind of data which can be delivered independently of the above noted restrictions. That is, such data can be delivered at any nominal rate, at any piece-wise nominal rate, and/or is insensitive to the relative movement of pieces of a constituent part of a given data stream. Such data can be a file, executable code, e-mail, a music file, video mail, an “EPG” (electronic program guide), a web page, etc. Generally, each data stream of the type noted above is not consumed in real-time, i.e., more or less as delivered, or if executed in real-time, is tolerant of pauses in delivery or presentation of the data stream. Hereinafter, such data or data streams are referred to as “best-effort” data or data streams to distinguish them from real-time program data.
The prior art teaches a satellite network for carrying one or more best-effort data streams with television signals to a remote site. At the remote site, another device receives the satellite signal and is capable of extracting one or more of the best-effort data streams for receipt thereat. The device of the remote site can have a telephone return path, including a modem that can connect via the Internet, or other wide area network, to the source of the satellite signal.
Another prior art satellite network teaches a network that solely delivers best-effort data packets to one or more remote sites. At the remote site, a device receives the best-effort data packets and determines if any are destined to other computers at the same remote site. This device transfers such data packets destined to the other computers at the same remote site onto a LAN. The other computers detect the data packets and selectively receive and process each packet destined to the respective computer. These computers can also transfer onto the LAN other packets for transfer back to the source of the received packets. These other packets can be intercepted by the same device which receives packets from the satellite, or a second device, for transfer back to the source via a modem and the Internet or other wide area network.
It is an object to provide an improved system that can easily control multiple nodes in a broadcast network that transmits best-effort data.
It is another object to control multiple nodes at remote sites which might not have a return path to the source of the best-effort data.